From what I understand, the Sol Nano units from AI are simply half of one of the larger units. The standard SOL units run 70 optics on the four outside pucks, and 40 degree optics on the four inside pucks.
I'd guess that the nano's probably have the 70 degree optics on pucks to help with coverage.
As far as MH vs LED goes, I'd like to think my opinion has a little bit of weight. I started my tank in August of '10 with a combination MH/T5 fixture. March of this year I had a serious outbreak of Cyano, and instead of replacing all the aged bulbs in my system, I decided to upgrade to the AI SOL Super Blues. I have three of the units over my 180, and I cant even run them at full power (I burned some acropora when first using the lights). The nuisance algae went away overnight. Shortly after switching over to the AI's everything in the tank looked better. The corals I had expanded more, and my hammer colored up more than it was under the metal halides.
The metal halides made the tank look 'brighter' but its obvious that the LED's are putting out far more usable light to the corals. The other thing I should mention is that i replaced roughly 1000 watts of light with just 225 Watts, and my actual usage is less because I'm only running them at 40%
The only real complaint I have about the AI's is the clumsiness of their controller, especially the knob you have to turn to make changes to the settings. There are times where I turn it to the right (or forward) and the setting actually changes backward. Realistically though, once my timers were set I haven't really needed the controller much, and you could always use one of those crazy controllers like the Reef Keeper.
I recommend the AI LED's to anyone that asks. Ed put 5 of them over the 'twins' after seeing them setup on my tank. I'm pretty sure Dana liked them over my tank as well.